Production of oil by in situ combustion



Dec. 31, 1957 H. o. DIXON 2,818,118

PRODUCTION OF on. BY IN SITU COMBUSTION Filed Dec. 19, 1955 IN VEN TOR. HENRY O. DIXON A r Tom/g rs 1.51MB? rnonucrroN or on, BYlN-SI'I'U'CQMBUSTION Hen i n, Bar losvi e, k a s n to Phillips Petroleum Company, a .corporatiou of Delaware ApplicationDecember 19, 1955, Serial No. 553,788 19 C aims- .(Cl. -16+111 i n ion relates to a p o ess rnic hod, or. t IQC Q Y or p qd tio o flui yd oca bons r nde und o ma on contain n h d ocarb n mat ial as applied to primary, secondary, or tertiary; recovery progl rfi t? ec e ofoil fr m-unde gr und Que-Containing o ma on by n itu om us on tech ques hasrecently o nt use he c n en ona m tho .or. techniq entails initiating combustion in the formationamund-a wellbore by some suitable means such as by'injecting ho ai at combustion-supporting temperatures. into the o ho e o a to t blis a ombust on zone surround ing the boreholeand continuing the injection; f l. .0 other free oxygen-containinggas so as to drive: thecoma n front a ia y utwardly. from the i j ti w l bore. In the copending patent application of. A. F. Bortnzzi and M- k. .N- 42, 88, filed October 24, 1 95 5, an ,oil r covery pro e s is disclosed-and claimed, wherein a combustion zone is established ina fracture in a formation containing oil and the combustion area is advancedsubstantiallyver ically thru the formation to a higher or lower level therein from which. the fluid y roca b n produ ed y e ombu tion .are recover d or thru W iCh combustion supporting. is fedto the combustion front so as to produce the fluid hydrocarbons in the well thru which combustion was. initiated. Operation in accordance with the process of said application is highly advantageousin certain oilbearing formations.

invention is concerned with amethod of rapidly establishing a thin horizontally extending heatedarea or combustionzone inan oil-bearing formation whichnis p t lna vefi cti e in onjunction with-the. process de.- scribed in the aboveridentified patent application.

-P IY obje of he invention is .to-provide amethod fo rapidly heating a selected area ofan underground formation. Another object of the invention isto provide a method for quickly establishing anextendedcombustion zone in an oil-bearing formation. Another. object is to, provide .a process for initiating a thinhorizontally extended combustion zone, in an oil-bearingformation. A further object of the, inventionis toprovidean improved method of oil recovery byin situ combustion. It is also an object of the invention, toprovide-an improved method for initiating vertical drive .in. an oil re.- covery process utilizing in, situ combustion. Other obio ts of the invention l. become, apparent from. aconsideration of the accompanying disclosure.

The broadest aspe t of .the invention comprises depositing small particles of solid combustiblematerial, having. good electrical conductance, intheinduced or natural fractures surrounding awell bore in an oil-bean ingformation soas-to, provide a path:- of conductance or circuit thru the fracture between, electrodes positioned in spaced apart relation in boreholes or wells connected with the fracture, and passing suflicient current from one electrod tothe other thru the,particulate. circuit so as to, heat the particles to ignition temperatureof thehydrocarbon'in the. formation andipreferably-of theparticulate material. itself and supplying free oxygen to the heated area so as to cause combustion therein. Fluid hydrocarbons driven out of the formation by the combustion process are then recovered at a. higher or lower level in the formation from a Wellpenetrating the formation, and preferably fractured, so as to provide a sub stantially vertical flow. path from the combustion area or zone to the fracture extending outwardly from the producing well.

vGenerally the producing well is positionedintermediate the wells in which theelectrodes are positionedto-initiate combustion. The electrodes-may comprise conventional electrode materials such as copper, carbon, etc. The well casing may alsobe used as the electrode for that particular Well. In one type of operating pattern a centrally positioned well is provided with an electrode connected to one terminal of the power source and-a group of surrounding adjacent wells are provided with. electrodes each connectedwith the opposite terminal of the-power source. With this arrangement at least the major; portion of the area intermediate thecentral, Well and the surrounding wells is heated to at least thevignitiontemperature of the hydrocarbon in the formation with proper application of the invention. This method effects greater heating. in-thevicinity of the central. well and thus is advantageousin fluidizingand driving hydrocarbons from the formation around the; central well, particularly. in applications which depend upon heating'without combustion to effect production, alone, or followed by air injection and in situ combustion.

The process of the invention is applicable to merely heating the formation so as to drive out:hydroca-rbons by vaporization, lowering-the viscosity of the entrapped hydrocarbon oil, and otherwise fluidizing and causinghy, drocarbons to flow into a producing well. It is, however, particularly advantageous in assisting or supplementing in situ combustion.

After; combustion has been initiated and the combustion area has been movedvertically in the formation a substantial distance by injection ofair into the forma tion thru the boreholes in which the electrodes are positioned, it is feasible to reverse the, flow of air in the manner disclosed and claimedin the copending U. S. patent application of John Marx, S. N. 526,388, filed August 4, 1955, so as to cause the combustion front to move counter-currently to the flow of air and produce the fluid hydrocarbons driven out ofthe formation thru the boreholes thru which combustionwas initiated.

Materials suitable for use as electrical conductors and as combustible materials in accordance with the invention comprise metals, such. as magnesium, zinc, and aluminum which burn readily in the presence of free-oxygen when raised to high temperatures. It is also feasible to utilize small pellets or grains of metals, such as iron, composited with an oxygen donor, such as .manganese dioxide, which supports the combustion. of the'ironwhen the same is raised to red hot temperature. Carbon particles are also operable in setting up a circuit. Any metal particles may be used where the operation involves merely heating up the formation.

The finely divided combustible material is conveniently introduced to the fractures surrounding a well and con.- necting with fractures from anadjacent wellwby mixing the same with a granular propping material such as sand introduced during the final stages'of the fracturingsprocedure. The use of such a combustible-material as mag. nesium provides substantiallymore heat to.initiate-the combustion process in the in situ; combustion method because of its high heat of combustion. To. illustrate, the heat. of formation. of, magnesium oxide.-is.145;76 kilo-./ cal. while that of carbon, dioxide is 94.385 kilo. /cal. The heating or. quantity of 'heat produced by -the combustible material is readily controllable by controlling the quantity of material introduced to the formation such as by mixing with the propping sand. The magnesium powder may be mixed with one or more metals such as copper, aluminum, zinc, or iron together with the propping sand. Separation of the metal particles by the sand grains causes arcing between metal particles and thus additional heating, thereby causing the surrounding hydrocarbons to become ignited in the presence of free oxygen. It is,also feasible to substitute metal particles of suitable size for sand as the propping material. In one embodiment of the invention suificient powdered conductive material is deposited in the fractures to substantially coat the walls thereof. Powdered material and granular metals (as propping material) may be combined in a single application in which case the granular metal not only functions as propping material but also in the heating step.

Where in situ combustion is practiced air is injected at any convenient time to be present when ignition conditions exist so as to support the intended combustion and the flow of air is continued after combustion is initiated thereby continuing the combustion and building up a heat reservoir in the formation whereby fluidized hydrocarbons are driven from the combustion area and are produced in a well or borehole penetrating the formation at a higher level therein.

A more complete understanding of the invention may be had by reference to the accompanying drawing which shows a schematic arrangement of wells penetrating a formation and provided with apparatus for effecting the invention. Referring to the drawing, wells and 12 penetrate an oil bearing formation 14 to a lower level therein. Well 16 is positioned intermediate Wells 10 and 12 and penetrates to a higher level in formation 14. The various wells shown are provided with conventional casing 18 and well 16 is provided with tubing 20 which functions in conventional manner in producing the hydrocarbon driven vertically thru the formation to the level of the bottom of borehole or well 16.

Electrodes 22 and 24 are positioned in wells 10 and 12, respectively, and are connected by conducting lines 26 and 28, respectively, with the terminals of a suitable power source, e. g., generator 30. Generator 30 is preferably an alternating current generator but it is also feasible to utilize a direct current generator. Electric cables 26 and 28 pass through a sealing-lubricator device 32 and 33, respectively, at the well head, and over pulleys 34 and 35, respectively, suspended by means not shown so as to assist in manipulating the cable and electrodes upon insertion and removal from the well. Winch devices 36 and 37 are utilized in raising and lowering their respective electrodes and cables. Contact between the cable in each instance and the generator terminal is made thru conductor arrangements 38 and 39. The Well heads are provided with the usual sealing means and adapters and with air conduits 40, as well as with conventional producing equipment. Line 42 on well 16 may be utilized for air introduction when utilizing inverse air injection technique, in which case Wells 10 and 12 become producers.

In practicing the process of the invention, formation 14 is fractured thru well or boreholes 10 and 12 so that communication is established between the well bores thru a fracture such as 42 and/or 44. A fracture at a higher level in the formation may also be effected surrounding well 16 although with formations of relatively high permeability, it is not essential to fracture the formation around well 16 in order to recover fluidized hydrocarbon driven from the combustion area. During the fracturing process, particularly in the final stages thereof, when the propping sand and/ or other propping agent is introduced to the fractures, the combustible particulate material is admixed with the propping agent in suflicient quantities to provide a deposit in. the fracture of closely spaced particles and sufficient potential heat upon combustion to provide the desired heating for the formation when burned with air. Current is passed from current source or generator 30 thru the conducting cables 26 and 28 to electrodes 22 and 24 so that the current passes from one electrode to the other thru the permeable connecting fracture so as to heat up the particles of conducting material deposited in the fracture and air is introduced thru either one or both wells 10 and 12 thru lines 40 to be present in the'forrnation when the temperature is at or above ignition temperature. When the heating effect of the current raises the temperature of conducting particles to ignition temperature of either the particles or of the adjacent hydrocarbon material combustion is initiated and upon continued introduction of air through wells 10 and 12, the combustion front is advanced vertically thru the formation and fluidized hydrocarbons driven from the combustion area and present in the formation are produced from well 16 in conventional manner. In instances where well 16 is provided with fractures such as 46 and/ or 48, the flow of hydrocarbons from fracture 42 and/or fracture 44 is substantially vertically to fracture 46 and/ or 48 from which most of the produced hydrocarbons flow horizontally into well 16. In operating the process without fracturing the formation around the borehole of wall 16, fluidized hydrocarbons driven out of the combustion area pass in a generally vertical direction thru the pores of the formation and find outlet in the borehole of well 16 where it penetrates the formation. In applications in which the in situ combustion is not to be effected and production is by merely heating up the formation to effect heat and/ or vapor drive, introduction of air or free oxygen is omitted.

The technique or procedure just described may be applied in as many boreholes and in as many different locations in a formation as desired so as to produce as much of the formation as feasible and/or desirable. After establishing a combustion area in a formation in the manner described, it is also feasible to advance the combustion front in the desired direction by inverse air injection or by inverse air injection alternated with direct air injection.

In utilizing inverse air injection in producing oil with the arrangement of wells shown in the drawing, after combustion is initiated in fracture 42 and/or 44 and the burning is continued so as to establish a substantial heat reservoir by injection of air thru lines 40 into walls 11 and 12, the flow of air is reversed so that air is now injected thru well 16 and the fluidized hydrocarbons driven out of the combustion area are produced thru wells 10 and 12 by conventional pumping or recovery means. Inverse air injection may also be initiated by injection of air thru well 16 ab initio.

The invention described provides the advantage of a much larger initial combustion area than is obtainable by known methods of combustion initiation in situ combustion techniques. It is also highly effective in building up a substantial heat reservoir which permits early reversal of the direction of air when it is desired to use the inverse air injection technique and also permits inverse air injection ab initio, as described.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. In a process for recovering hydrocarbons from a gas-pervious underground formation containing same comprising horizontally fracturing said formation at a selected level thru a well therein; initiating combustion of hydrocarbon in and adjacent said fracture so as to drive fluid hydrocarbons out of the resulting combustion zone; and recovering said fluid hydrocarbons thru a production well at a substantially different level in said formation whereby vertical drive of fluid hydrocarbons is effected; the improvement comprising introducing into the resulting fractures particles of a solid combustible material which is a good conductor of electricity; passing an electric current between said particles so as to heat same to ignition temperature, and supplying a free-oxygen-containing gas to the fractured area so as to cause ignition of said particles and the hydrocarbon in said formation.

2. The process of claim 1 wherein said solid material comprises metallic magnesium.

3. The process of claim 1 wherein said solid material comprises metallic aluminum.

4. The process of claim 1 wherein said solid material comprises a mixture of powdered iron and an oxygen donor which supports combustion of the iron.

5. The process of claim 4 wherein said oxygen donor comprises manganese dioxide.

6. A process for igniting hydrocarbon material in a gas-pervious underground formation containing same so as to establish a thin horizontally extended combustion zone, which comprises horizontally fracturing said formation at a selected level in a well therein; introducing into the resulting fractures particles of a solid combustible material having good electrical conductance; passing an electric current in a circuit from particle to particle thru said material in said fractures so as to heat same to ignition temperature; supplying free oxygen to the heated area so as to cause combustion of said particles and of the adjacent hydrocarbon and initiate a thin horizontally extended combustion zone in the formation.

7. The process of claim 6 including the steps of fracturing said formation at a different level in a second well in said formation and causing the combustion zone to move toward said different level.

8. The process of claim 7 wherein said combustion zone is moved toward said different level by injection of air to said formation at said different level to cause countercurrent movement of air and said combustion zone.

9. The process of claim 6 wherein said solid material comprises metallic magnesium.

10. The process of claim 6 wherein said solid material comprises metallic aluminum.

11. The process of claim 6 wherein said solid material comprises a mixture of powdered iron and an oxygen donor which supports combustion of the iron.

12. A process for igniting hydrocarbon material in a gas-pervious underground formation containing same so as to establish a thin horizontally extended combustion zone, which comprises horizontally fracturing said formation at a selected level in a first well therein; horizontally fracturing said formation at said level thru a second well therein; introducing into the resulting fractures particles of a solid combustible material having good electrical conductance so as to provide a circuit from particle to particle between said first and second wells; passing an electric current thru said circuit so as to heat said particles to ignition temperature; and supplying free oxygen to the heated area in said fractures so as to initiate combustion of hydrocarbon in said formation in a thin horizontally extended area.

13. The process of claim 12 wherein said solid material comprises metallic magnesium.

14. The process of claim 12 wherein said solid material comprises metallic aluminum.

15. The process of claim 12 wherein said solid material comprises a mixture of powdered iron and an oxygen donor which supports combustion of the iron.

16. The process of claim 12 including the step of recovering fluid hydrocarbons produced in said combustion area thru a third well in said formation intermediate said first and second wells.

17. The process of claim 16 wherein said formation is fractured thru said third well at a higher level therein than the fractures connecting said first and second wells and the combustion area is advanced toward the higher level fractures.

18. The process of claim 12 wherein said particles are introduced to said fractures, together with propping sand, during the fracturing step.

19. A method of heating an underground gas-pervious oil-bearing formation to produce same comprising depositing particles of metal in the fractures of said formation so as to form a path for current between at least a pair of wells in said formation; passing an electric current thru said path so as to heat and burn said particles and oil in said formation and thereby drive fiuid hydrocarbons therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,301 Pitman Apr. 13, 1943 1,372,743 Gardner Mar. 29, 1921 1,784,214 Workman Dec. 9, 1930 2,630,307 Martin Mar. 3, 1953 

1. IN A PROCESS FOR RECOVERING HYDROCARBONS FROM A GAS-PERVIOUS UNDERGROUND FORMATION CONTAINING SAME COMPRISING HORIZONTALLY FRACTURING SAID FORMATION AT A SELECTED LEVEL THRU A WELL THEREIN; INITIATING COMBUSTION OF HYDROCARBON IN AND ADJACENT SAID FRACTURE SO AS TO DRIVE FLUID HYDROCARBONS OUT OF THE RESULTING COMBUSTION ZONE; AND RECOVERING SAID FLUID HYDROCARBONS THRU A PRODUCTION WELL AT A SUBSTANTIALLY DIFFERENT LEVEL IN SAID FORMATION WHEREBY VERTICAL DRIVE OF FLUID HYDROCARBONS IS EFFECTED; THE IMPROVEMENT COMPRISING INTRODUCING INTO THE RESULTING FRACTURES PARTICLES OF A SOLID COMBUSTIBLE MATERIAL WHICH IS A GOOD CONDUCTOR OF ELECTRICITY; PASSING AN ELECTRIC CURRENT BETWEEN SAID CPARTICLES SO AS TO HEAT SAME TO IGNITION TEMPERATURE, AND SUPPLYING A FREE-OXYGEN-CONTAINING GAS TO THE FRACTURED AREA SO AS TO CAUSE IGNITION OF SAID PARTICLES AND THE HYDROCARBON IN SAID FORMATION. 